1. Field of the Invention
This invention relates to ignition circuits and, in particular, to a high performance ignition circuit having minimal components and maximum performance characteristics and life.
2. Description of the Prior Art
The conventional automotive ignition circuits are based on the Kettering circuit which employs make-and-break contacts mechanically actuated by a cam on a distributor shaft which is driven by the engine. These contacts are in the primary winding circuit of the ignition coil to interrupt the circuit through the primary windings, collapsing the magnetic field of the coil and inducing high voltage pulses in the secondary windings. This circuit is subject to the mechanical shortcomings of the make-and-break contacts which limit its acceleration and top engine speed characteristics. Additionally, the maximum voltage induced in the secondary windings is often less than the optimum voltage for efficient engine firing.
The shortcomings of the conventional make-and-break contacts of automotive ignition systems have led to development of various solid state ignition systems including capacitor discharge systems in which a capacitor is charged, often in a regenerative manner, by a circuit which uses the timing pulses of the conventional make-and-break contacts and which uses a switching device such as a silicon controlled rectifier to discharge the capacitor through the primary windings of the ignition coil. These units have been employed successfully to increase the high voltage output from an ignition coil and to increase the limiting engine speed above that attained with conventional ignition systems. Capacitive discharge systems, however, have been subject to failure of critical circuit components and are relatively expensive to install and maintain and require alterations in the ignition coil connections which prohibit use of conventional engine instruments such as tachometers and ignition scopes without the use of auxiliary or accessory equipment.
There presently exists an unsatisfied demand for a reliable and relatively inexpensive ignition system having high performance characteristics, typically capable of producing from 20 to about 30 kilovolt ignition pulses in the secondary windings and engine speeds of 10,000 rpm. or greater. Desirably, such an ignition circuit should be useful with the conventional automotive ignition coil which has a ratio of secondary to primary turn windings of about 100/1. Desirably, such an ignition circuit should also be useful without any alterations in the ignition coil terminal connections, thereby permitting use of conventional engine instruments and, most preferably, useful in combination with a magnetic pulse generator, thereby freeing the ignition circuit from the mechanical shortcomings of the conventional make-and-break contacts.